Efficient and stable perovskite solar cells based on a biopolymer internal encapsulation strategy

<p indent="0mm">Perovskite solar cells (PSCs) have emerged as strong contenders in next-generation photovoltaic technologies, owing to their exceptional power conversion efficiency (PCE), low-cost fabrication processes, and tunable optoelectronic properties. In recent years, PSCs have achieved impressive laboratory-scale efficiencies, rivaling or even surpassing traditional silicon-based solar cells. However, despite these promising advances, the practical deployment and commercialization of PSCs remain significantly limited by critical challenges—chief among them are environmental instability and lead leakage. Perovskite materials are inherently sensitive to moisture, oxygen, heat, and UV light, which can lead to rapid degradation of device performance. Additionally, the presence of toxic lead in the perovskite layer raises serious concerns about potential environmental contamination and human health risks, particularly if the device is damaged or disposed of improperly. To address these pressing issues, this study proposes an internal encapsulation strategy using two bio-based polymers—polydopamine (PDA) and Chitosan—as protective interfacial layers within the PSC device architecture. These materials are selected for their excellent biocompatibility, chemical versatility, and environmental sustainability. When introduced into the device structure, both PDA and Chitosan contribute to improved perovskite film quality by promoting better crystallinity, passivating trap states, and reducing non-radiative recombination losses. They also function as physical and chemical barriers, significantly suppressing the diffusion of lead ions under harsh environmental conditions. Among the two candidates, PDA demonstrated clearly superior encapsulation performance. This advantage is attributed to PDA’s unique molecular characteristics, including a multi-site distributed molecular framework that facilitates the formation of a synergistic coordination network. This network promotes the formation of stable bonds under mild, non-destructive processing conditions, effectively passivating surface defects without compromising the integrity of the perovskite lattice. Furthermore, PDA’s mussel-inspired molecular structure allows it to undergo spontaneous self-polymerization on a wide range of surfaces, forming highly uniform, dense, and conformal coating layers. This enhances both the mechanical robustness and moisture resistance of the encapsulation layer, outperforming traditional materials such as Chitosan in long-term stability tests. Performance evaluations revealed that PSCs encapsulated with PDA exhibited outstanding environmental resilience and device stability. Under simulated acid rain conditions, PDA encapsulation reduced lead leaching from <sc>13.2 mg/L</sc> (in unencapsulated samples) to just <sc>7.2 mg/L.</sc> Under 85% relative humidity, PDA-encapsulated devices retained 87.6% of their initial PCE after 500 hours of continuous operation. Additionally, the optimized PDA-encapsulated devices achieved a PCE of 24.09%, significantly higher than the 21.11% observed in the unprotected control group. Moreover, cytotoxicity assays confirmed the biological safety of PDA, further supporting its suitability for environmentally responsible and human-safe photovoltaic applications. Importantly, the encapsulation process is simple, cost-effective, and scalable, demonstrating compatibility with large-area fabrication techniques. In conclusion, this work presents a feasible, scalable, and eco-friendly internal encapsulation approach for enhancing the stability and safety of PSCs. By leveraging the unique chemical and structural features of PDA, the strategy provides a promising pathway toward the commercialization of high-efficiency, stable, and sustainable perovskite-based solar energy technologies.